1. Field of the Invention
The present invention relates to an automobile airbag system and, in particular, to the structure of a lid for an airbag system.
2. Description of Related Art
Typically, passenger side supplemental restraint systems, which are generally called airbag systems, have the main body of an airbag system located inside an instrument panel and an airbag lid provided on the front of the airbag system main body, i.e. on the side of an opening of the airbag system main body through which an airbag inflates and expands. This airbag lid is located in an opening formed in part of the instrument panel extending below a front windshield glass and is hinged at its top to the instrument panel so that, when the airbag inflates and expands, the airbag lid is flipped upward about the hinged top by the inflating and expanding airbag. Such an airbag system is known from, for instance, Japanese Unexamined Patent Publication No. 4-59450.
On the other hand, in order for the airbag lid to break easily so as to relieve the energy of an impact when the airbag lid is flipped up and smashes against the front windshield glass, the airbag lid is made easy to break. Such a flip-up airbag lid is known from, for instance, Japanese Unexamined Utility Model Publication No. 4-89449.
In recent years, it is demanded or required by rule or regulation that instrument panels must be structured so that they do not make an impact larger than a specific force or strength on a passenger's head. In other words, the instrument panel, when hit or struck by the passenger's head, does not cause the passenger's head to be subjected to or experience negative acceleration greater than a specific level. For the fulfillment of or compliance with this rule or regulation, the flip-up airbag lid is structured such that it has an increased rigidity so as to absorb the energy of an impact gradually during its deformation due to being struck a blow by a passenger's head. Accordingly, the flip-up airbag lid is required to meet two somewhat conflicting requirements that govern structural rigidity and easy breakage.